It is known in the art relating to manufacturing axle mounted differential gear assemblies to preload tapered roller bearings that support the pinion shaft. During manufacturing an operation is performed in which a pinion shaft nut is tightened on the pinion shaft to force a universal joint yoke to partially collapse a collapsible sleeve positioned between a pair of spaced tapered roller bearings that support the pinion shaft. Bearing preload is determined by measuring the torque required to rotate the bearings after the pinion shaft nut is tightened.
The torque required to tighten the pinion shaft nut and collapse the sleeve is generally in the range of about 100 lb-ft. The torque required to rotate the bearings at the desired preload is generally less than 10 lb-ft.
To minimize the cycle time to perform the tightening and preloading operation it is desirable to measure the drag torque of the rotating pinion shaft while the pinion shaft nut is being tightened. Subtracting the rotating pinion shaft torque from the pinion shaft nut torque theoretically yields the bearing drag torque but presents the problem of having to subtract two large variables to obtain a small value.